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Charlie Materials > Concrete > Flashcards

Concrete Flashcards

1
Q

What are Clinkers?

A

Cement raw materials finely ground and carefully proportioned before heated to temperatures from 2,000 to 3,000 degrees (F) to from hard pellets

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2
Q

What is the composition of concrete

A

Mixture of aggregates and often controlled amounts of entrained air and held together by a hardened paste made from cement and water

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3
Q

What is air entrainment

A

Air entrainment is the intentional creation of tiny air bubbles in concrete.

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4
Q

What are the 3 components of concrete

A

Water
Aggregate: Sand/gravel
(Portland) Cement

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5
Q

What is the most commonly used cement in the military

A

Portland Cement

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6
Q

What is the chemical reaction called when water and cement mix?

A

Hydration

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7
Q

What is the optimal temperature for cement hardening

A

73 degrees

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8
Q

What 2 functions does water play in concrete

A
  • Effect hydration

* Improve workability

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9
Q

What determines the strength of concrete

A

ratio of cement to water

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10
Q

Does more water or less water strengthen concrete

A

less water

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11
Q

Aggregates make up what total volume of finished cement

A

60-80%

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12
Q

What is the primary purpose of aggregate in cement

A

To gain economy

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13
Q

What are the most common contaminating materials in concrete

A

dirt, clay, salt

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14
Q

What are the rules of thumb for the maximum size aggregates should be in concrete

A
  • The maximum size should not exceed 1/5 the minimum diameter of a wall or similar structure
    – Not to exceed 1/3 the slab thickness
    – Not to exceed 3⁄4 of the clear space between reinforcing bars
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15
Q

What are the 5 types of Portland cement

A 
– Type I (Normal Portland)
– Type II (Modified)
– Type III (High early)
– Type IV (Low heat)
– Type V (Sulfate resistant)
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16
Q

What are 3 other cements

A 
• White Portland
• Air Entrained (Type I, II, III)
• Oil Well Cements
• Waterproofed Portland cements
• Plastic cement
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17
Q

What does a bag of Portland Cement weigh

A

– Bags-94 lbs (contains one cu ft of loose

measurement)

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18
Q

How many and what are the types of CONCRETE

A
  • Reinforced
  • Prestressed
  • Precast
  • Lightweight
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19
Q

What are the benefits of precast concrete

A 
- In dead-loads making savings in
foundations and reinforcement
- Improved thermal properties
- Improved fire resistance
- Savings in transporting and handling pre- cast units on site
- Reduction in formwork and propping
20
Q

What are the disadvantages of concrete

A
  • Low tensile strength
  • Expands and contracts
  • Shrinks when dry
  • Heavy
21
Q

What do construction joints do?

A

join concrete that is paved at different times

22
Q

Do construction joints allow for movement of concrete members

A

No

23
Q

What do contraction joints do

A

control natural cracking from stresses caused by concrete shrinkage, thermal contraction, and moisture.

24
Q

At what angel are transverse contraction joints cut

A

At a right angle to the pavement centerline and edges.

25
Q

What do isolation joints do

A

separate the pavement from objects or structures, and allow independent movement of the pavement, object or structure without any connection that could cause damage.

26
Q

Where are isolation joints used

A

where a pavement joins sidewalks and buildings, and intersects other pavements or bridges.

27
Q

What do expansion joints do

A

Permit volume change movement of a concrete structure or member.

28
Q

What is the minimum width of an expansion joint

A

1/4′′ wide

29
Q

1 person can manually mix approximately how much concrete per hour

A

1 cubic yard

30
Q

Describe the hand mixing sequence of concrete

A

Three part gravel, then Two part sand (mix dry 3x), then One part Portland cement, and add water

31
Q

Project Volume (PV) = ?

A

length x width x height x number of pours

32
Q

Loss Factor = ?

A

if PV 5400 cubic ft (or 200 cubic yards), add 5% to project

33
Q

Loose Volume (LV) = ?

A

LF x 1.5 (and round up)

34
Q

Equation for calculating cement from Loose Volume (LV)

A

1/6 x LV = number of bags of cement (rounded up)

35
Q

Equation for calculating sand from Loose Volume (LV)

A

2/6 x LV = cubic feet (yards) of cement
OR
LV/3 = cubic feet (yards) of cement**

**This may be “funny” math

36
Q

Equation for calculating gravel from Loose Volume (LV)

A

3/6 x LV = cubic feet (yards) of gravel
OR
LV/2 = cubic feet (yards) of gravel

37
Q

Equation for calculating gallons of water from number of bags of cement

A

Water (in gals) = number of bags of cement x 8

38
Q

Forms must be what in order to hold concrete properly until it sets

A

Tight, rigid, and strong

39
Q

What materials are forms usually made of

A

Wood, metal, earth, fiber

40
Q

What are the elements of wooden forms

A

Sheathing, batten, yoke, and bracing

41
Q

What does the yoke do in a wooden form

A

ties the top of sheathing together in column form

42
Q

What is the difference between a vertical keyway and a horizontal keyway

A

one is vertical and the other is horizontal

43
Q

What is the maximum rate of filling concrete to avoid excessive pressure on form

A

4 ft per hour

44
Q

How deep does the land under a slab need to be moistened (if plastic isn’t being used as a barrier between the slab and the ground)

A

6 inches

45
Q

Slabs which will support load bearing walls must be what?

A

Reinforced with rebar

46
Q

True or False: Rebar in slabs must sit above the frost line

A

False. Must be below frost line

Charlie Materials (40 decks)

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